1. Field of the Invention
The present invention relates to surgical apparatus, and more particularly, to apparatus for performing endoscopic surgery.
2. Description of the Prior Art
Over the past decade, arthroscopy has become one of the most rapidly developing techniques in orthopaedic surgery. Arthroscopic meniscectomy has largely replaced conventional meniscectomy. Carpal tunnel syndrome, or tardy median nerve palsy, which is caused by the compression of the median nerve within the carpal tunnel, requires the surgical release of the transverse carpal ligament. Until recently, the procedure was performed by open surgery. An incision of several centimeters in the wrist area was necessary to avoid injury to the median nerve.
Endoscopic approaches to carpal tunnel surgery are emerging as satisfactory replacements for the open surgical procedures. A subcutaneous endoscopic procedure is described in I.Okutsu et al., "Endoscopic Management of Carpal Tunnel Syndrome," Arthroscopy: The Journal of Arthroscopic and Related Surgery 5(1):11-18 (1989). The Okutsu et al. procedure employs a clear plastic outer tube, or sheath, and a standard arthroscope. The tube has a bevel-shaped barrel about 100-175 mm in length and about 6 mm in diameter. The arthroscope is used in conjunction with a video-camera, recorder and light source. Following the incision of the wrist area, an obturator is inserted into the carpal tunnel from the radial side of the palmaris longus tendon to help guide insertion of the videoarthroscope. The obturator is then removed and the clear plastic tube inserted. The videoarthroscope is then advanced into the tube. The endoscope is removed and reinserted on the opposite side of the palmaris longus tendon. A retrograde hook knife is thereafter inserted along the side of the clear plastic tube to cut the transverse carpal ligament. The clear plastic tube is described more fully in Okutsu, U.S. Pat. No. 4,819,620. The tube has a closed, generally rounded distal end and an open proximal end through which the videoarthroscope and/or a knife may be inserted. A slot is provide along a portion of its length through which the cutting edge of the knife projects to cut the desired site. It is believed that visualization may be distorted because of the curved clear wall of the tube.
Another endoscopic procedure, known commercially as the Agee Carpal Tunnel Release System, employs a videoscope, a disposable knife cone, a hand piece with a trigger, three curved obturators and one freerer. The obturators are used consecutively to make a channel The hand piece, which has an elongate shaft portion, is then inserted into the channel via the hook of hamate. When in the desired position, the trigger is pressed to activate a knife blade which pops up through a window in the elongate shaft. The hand piece is then drawn back to cut the ligament. The exposed blade cannot be viewed during the procedure.
Storz, U.S. Pat. No. 4,656,999 describes an endoscope in which there is a strip blade at the distal end which can be moved in a slideway at a relatively small distance in front of the lens. Boebel, U.S. Pat. No. 4,620,547 describes an instrument which includes an outer shaft which is closed at its distal end and has an opening in its side wall close to the distal end, and an inner shaft which is movable axially within the outer shaft, for carrying an endoscope. The endoscope may have a cutting edge at its distal end so that tissue drawn through the side opening of the outer shaft may be severed while being observed through the endoscope.
An object of the present invention is to provide an endoscopic procedure and a system for performing the procedure which permits the direct, undistorted visualization of the incision site while the cut is being made. It is a further object of the present invention to provide such a procedure and system for performing the procedure which creates a clearly defined unobstructed work space to enhance visualization and accuracy of the endoscopic procedure.